Removal of wax from hydrocarbon oil



Patented Aug. 7, 1934 1,969,670 REMOVAL OF WAX 550M HYDROCARBON Bernard Y. McCarty, Beacon, N. Y., and William E. Skelton, Cambridge, Texas Company, tion of Delaware No Drawing. Application Serial No.

Mass., assignors to The New York, N. Y.,*a corpora November 30, 1931 578,210

4 Claims. (Cl. 196-19) This invention relates to the removal of wax from hydrocarbons and more particularly to'an improved process for the removal of paraflin from lubricating oil fractions derived from petroleum.

The invention contemplates a process of dewaxing wax-containing lubricating oil fractions by'filtration at low temperatures, wherein the wax-containing oil is mixed with a wax-precipitating liquid medium composed of a solvent liquid or mixture of solvent liquids which is completely miscible with, and exerts a substantially complete solvent action upon, the oil at the temperatures at which the wax constituents are precipitated from the oil in solid form and which has substantially no solvent action on the solid hydrocarbons at such temperatures. The resulting mixture is then chilled to precipitate the solid hydrocarbons which are removed by filtration.

More specifically the invention contemplates mixing with the lubricating oil fraction a waxprecipitating liquid medium composed of a mixture of amylene dichloride and methyl ethyl ketone.

An object of this invention is to effect dewaxing of paraflin-containing hydrocarbon oils with an improved type of solvent liquid composed of a mixture of solvents having selective solvent properties between the oil and the wax constituents and which, in addition, retains its selective solvent properties at relatively low temperatures whereby the precipitationof the wax from the mixture, particularly in the case of mixtures with relatively viscous oils, is effected in a more readily filterable form. At the same time, a high yield of dewaxed oil is obtained.

A further object has been to develop a solvent liquid which possessed the foregoing properties at relatively low temperatures and which is, therefore, adaptable for the manufacture of lubricating oils having pour'tests of 20F. and lower.

A selective solvent suitable for the foregoing dewaxing operation, and particularly when composed of two or more organic solvents, must retain its homogeneity and its property of remaining completely miscible with the liquid hydrocarbon constituents of the mineral oil at temperatures substantially well below 0 F. Complete miscibility is necessary in order to prevent separation of such liquid hydrocarbons from the solution. 'Such separated liquid hydrocarbons materially increase the viscosity of the solution, thereby tending to reduce the filtering rate to a point where the operation is not economical. In addition, the presence of this separated liquid gives rise to a condition which is productive upon desired pour test of the containing substantial maximum yield of defiltration of a wax cake amounts of oil so that the waxed oil is not realized.

It is essential that such a solvent mixture remains completely homogeneous at these low tem- 00 peratures and not exhibit any tendency for any of its components to separate from the mixture. Upon separation of one of the components from the solvent mixture, the ratio of the components remaining in the mixture is' altered, thereby 66 changing its selective solvent properties so that the wax constituents will not be completely precipitated and/or appreciable amounts of the liquid hydrocarbon may separate from the solution due to the resulting lack of complete miscibility 70 on the part of the solvent with the oil owing to its altered condition.

Extensive investigation has demonstrated that a solvent liquid or solvent mixture satisfactory for use as a wax-precipitating medium in the 76 dewaxing of wax-containing hydrocarbon oils must possess, among other things, low absolute viscosity and low 'viscosity temperature coefficient, high oil solubility at low temperatures, low wax solubility at low temperatures, low freez- 80 ing point, and also possess the property of precipitating wax in a. readily filterable condition.

Accordingly after investigating various solvent liquid mixtures, it has been found that a mixture of amylene dichloride and methyl-ethyl- 86 ketone possesses the foregoing combination of properties, thereby rendering it superior to the solvent liquids or liquid mixtures hitherto used in the art and, therefore, particularly well adapted as a wax-precipitating medium for use in the 90 manufacture of low pour'test paraflln base lubricating oil. The relative proportion of these liquids to each other, as well as that of the resulting solvent mixture to the oil, may be varied as desired, depending upon the nature of the oil undergoing treatment.

Thus when dewaxing a lubricating distillate fraction having a viscosity of around 70 to 80 Saybolt Universal seconds or higher at 210 F., about thirty parts of the oil may be mixed with about seventy .parts of a solvent mixture composed of around 60% of amylene dichloride and 40% of methyl ethyl ketone. The resulting mixture is then chilled to about --10 F. or to a temperature corresponding substantially to the 106 resulting dewaxed oil,

following which it is subjected to filtration while still maintained in a cold condition to separate the precipitated wax constituents. Advantageously filtration may be carried out in the pres- I10 ence of a comminuted filter aid material which may be added to and commingled with the cold mixture or oil, solvent and suspended wax crystals. After removal of the solvent liquid from the-filtrate, the resulting lubricating oil will have a pour test of 0 F. or lower.

While the use of the foregoing solvent liquid mixtures has been described in connection with a lubricating distillate fraction of relatively high viscosity, it is contemplated that mixtures of these solvent liquids may be equally well employed with oils of various viscosity ranges. It is also contemplated that mixtures 01! these solvent liquids are not necessarily restricted to dewaxing distillate fractions but may also be'used in dewaxingvarious wax-bearing fractions of mineral oil.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

l. In the process of manufacturing low pour test lubricating oil from wax-bearing mineral oil substantially as described, the step comprising mixing with the oil a selective solvent liquid composed of amylene dichloride and methyl ethyl ketone in such proportions that the oil is substantially completely soluble at temperatures of the order of --l0 F. and the wax is substantially completely insoluble at such temperatures.

2. The process of manufacturing lubricating oil having a pour test of 0 F. or lower from wax-bearing mineral oil which comprises mixing the oil with a selective solvent liquid com-"- posed of, amylene dichloride and methyl ethyl ketone in such proportions that the oil is substantially completely soluble at temperatures of the order 0! l0 F. and the wax is substantially completely insoluble at such temperatures, chilling the mixture to a temperature of about 0 F. or lower to precipitate the wax constituents as solid hydrocarbons, and removing while maintained in "a cold condition the solid hydrocarbons so precipitated.

3. The process of manufacturing lubricating oil having a pour test of 0 F. or lower from waxbearing mineral oil which comprises mixing the oil with a selective solvent liquid composed of about 60% amylene dichloride and 40% of methyl ethyl ketone, chilling the mixture to a temperature oi! about -10 F. or lower to precipitate the wax constitutents as solid hydrocarbons, and illtering the mixture, while maintained in a cold condition to remove the solid hydrocarbons so precipitated.

4. The process of manufacturing low pour test lubricating oil from wax-bearing mineral oil comprising mixing with the oil a selective solvent liquid composed of amylene dichloride and 100 methyl ethyl ketone in such proportions that the oil is substantially completely soluble at temperatures of the order of -l0 F. and the wax is substantially completely insoluble at such temperatures, chilling. the mixture to a temperature at which the wax constituents are precipitated, and filtering the resulting mixture in the pressure of a filter-aid material and while maintained in a cold condition to remove the precipitated wax constituents and produce a desired low pour test 110 lubricating oil product.

BERNARD Y. McCARTY. WILLIAM E. SKELTON. 

